Joint physical layer security and PAPR mitigation in OFDM systems

ABSTRACT

Systems and methods for securing orthogonal frequency division multiplexing (OFDM) transmission of data are discussed herein. Computing devices can sense the signal strength of frequencies on an OFDM wireless channel. The computing device can determine which of the frequencies are fading frequencies failing below a threshold. A transmitting computing device can send artificial data on the failing frequencies and genuine data on the remaining frequencies. Artificial data can be designed to mitigate peak-average-power ratio (PAPR) to have an additional benefit without using extra resource.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Patent Application entitled“Joint Physical Layer Security and PAPR Mitigation in OFDM Systems”,having Ser. No. 15/276,838, filed Sep. 27, 2016, which is a continuationof U.S. Patent Application entitled “Joint Physical Layer Security andPAPR Mitigation in OFDM Systems”, having Ser. No. 14/870,464, filed Sep.30, 2015, and claims priority to, and the benefit of, U.S. provisionalapplication entitled “Joint Physical Layer Security and PAPR Mitigationin OFDM Systems”, having Ser. No. 62/141,978, filed Apr. 2, 2015, thecontents of which are incorporated by reference in their entirety.

BACKGROUND

The broadcast nature of wireless mediums can be susceptible to threatsregarding privacy and security of wireless communication. For example,an eavesdropper may be able to capture wireless signals. Depending onthe type of wireless transmission, these signals can be available from avariety of distances, for example several yards, a mile, or across theglobe. Data protection techniques can provide one form of security tocommunication. Encryption with a secret key is one method to concealdata. However, encryption techniques may not be sufficient for somescenarios, such as securely sharing a secret key with the intendednodes. Therefore, alternative means are needed to increase security. Forexample, physical layer security can provide enhanced security in thewaveform domain. Security measures dealing with the waveform domain canprevent the extraction of the actual data properly. An eavesdropper canbe prevented from extracting the actual data even if they can receiveentire transmissions.

A multiple-input multiple-output (MIMO) system can have enhancedphysical security by the addition of artificial noise to the actualsignal. The noise signal can be designed to fall in the null space ofthe channel matrix between the antennas of legitimate devices using theMIMO system. Artificial noise can be eliminated while the signal ispassing through the channel. Another device located in a different placehas a different channel matrix than a legitimate transmitter. Theartificial noise can distort the actual signal. The distortion of theactual signal can increase security. In a single-input single-outputsystem (SISO) for single carrier-frequency domain equalization (SC-FDE)waveforms, artificial noise can be added to fading frequencies. Forexample, the artificial noise can be added to the fading frequenciesinstead of adding artificial noise to the null space. Fading frequencyinformation can only be determined by legitimate transmitters. Forexample, an eavesdropper cannot separate the actual signal andartificial noise. As such, an eavesdropper can experience a significanterror. However, unlike SC-FDE, where data symbols are carried in thetime domain, OFDM systems carry data symbols in the frequency domain.Therefore, introducing a noise signal to an OFDM signal might notprevent eavesdroppers from detecting which frequencies are utilized andignoring transmissions on those frequencies since noise has a differentcharacteristic compared to the data.

In wireless communication systems, orthogonal frequency divisionmultiplexing (OFDM) can provide numerous advantages, for example OFDMcan transmit data with high bandwidth efficiency, OFDM can beimplemented with fast Fourier transformation (FFT), and OFDM can beequalized simply by exploiting the advantage of cyclic prefix (CP). Onthe other hand, OFDM signals can suffer from high peak to average powerratio (PAPR) caused by the parallel transmission because of thenon-linear characteristics of power amplifiers. An OFDM signal can benonlinearly scaled, and in-band interference can occur at thetransmitter.

DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the embodiments and the advantagesthereof, reference is now made to the following description, inconjunction with the accompanying figures briefly described as follows:

FIG. 1 is a drawing of a networked environment according to variousembodiments of the present disclosure;

FIGS. 2A and 2B illustrate frequency regions of data as seen by variousreceivers and transmitters according to various example embodiments;

FIG. 3 illustrates bit-error rates for various receivers andtransmitters according to various example embodiments;

FIG. 4 illustrates PAPR reduction performance according to variousexample embodiments;

FIGS. 5A and 5B are flow charts illustrating one example offunctionality implemented on a transmitting transceiver and a receivingtransceiver according to various embodiments; and

FIG. 6 illustrates an example schematic block diagram of a computingenvironment which can embody one or more of the system according tovarious embodiments.

The drawings illustrate only example embodiments and are therefore notto be considered limiting of the scope described herein, as otherequally effective embodiments are within the scope and spirit of thisdisclosure. The elements and features shown in the drawings are notnecessarily drawn to scale, emphasis instead being placed upon clearlyillustrating the principles of the embodiments. Additionally, certaindimensions or positionings may be exaggerated to help visually conveycertain principles. In the drawings, similar reference numerals betweenfigures designate like or corresponding, but not necessarily the same,elements.

DETAILED DESCRIPTION

In the following paragraphs, the embodiments are described in furtherdetail by way of example with reference to the attached drawings. In thedescription, well known components, methods, and/or processingtechniques are omitted or briefly described so as not to obscure theembodiments.

Although embodiments have been described herein in detail, thedescriptions are by way of example. The features of the embodimentsdescribed herein are representative and, in alternative embodiments,certain features and elements may be added or omitted. Additionally,modifications to aspects of the embodiments described herein may be madeby those skilled in the art without departing from the spirit and scopeof the present invention defined in the following claims, the scope ofwhich are to be accorded the broadest interpretation so as to encompassmodifications and equivalent structures.

Discussed herein is a technique for securing OFDM signals. In addition,the technique can also be enhanced to mitigate PAPR. The reduction ofPAPR can be accomplished without sacrificing additional spectralbandwidth. In contrast to introducing artificial noise, artificial datacan be inserted into modulated symbols since an eavesdropping device maybe able to determine the frequency location utilized as artificialnoise. By inserting artificial data into modulated symbols, aneavesdropping device can be prevented from detecting artificial datafrequencies.

In addition, the artificial data can be chosen to mitigate PAPR. Bychoosing PAPR mitigating artificial data, the PAPR can be reducedwithout consuming resources beyond those utilized for security. Theartificial data can be selected based on the data to be transmitted. Thedata signal can include genuine data that corresponds to the frequenciesthat meet the channel gain threshold. In one example, the genuine datais information to be transmitted from the transmitting device to thereceiving device.

The system can include an OFDM wireless channel that is between a pairof wireless transceivers. The wireless channel can include a pluralityof frequencies bands. For example, in OFDM multiple orthogonalfrequencies are used. A wireless transceiver can communicate over theOFDM wireless channel to another wireless transceiver. Each of thewireless transceivers can be configured to sense the signal strength orchannel gain of each frequency on the OFDM wireless channel. Thetransceivers can also be configured to determine which of thefrequencies meet a threshold, and this determination can be based on thesignal strength of each of the frequencies.

While the threshold can be predefined, in some embodiments, thethreshold can be set by a user of the system, and in other embodiments,the threshold can be negotiated between two devices. The threshold canbe based on the amount of data to be transmitted and/or the sensitivityof the data. For example, if a transceiver is to transmit a short andvery important data packet, the threshold can be higher.

The transmitting transceiver can be configured to generate artificialdata that reduces the PAPR of the resulting transmission. Thetransceiver can also initiate transmission of the resulting data signal.The resulting data signal can include the artificial data correspondingto frequencies that are determined not to meet the threshold. Theresulting data signal can include genuine data being mapped tofrequencies that are determined to meet the threshold.

With reference to FIG. 1, shown is a networked environment 100 accordingto various embodiments. The networked environment includes atransmitting device 103, a receiving device 106, one or moreeavesdropping device 109, and an OFDM wireless channel 112. Thetransmitting device 103, the receiving device 106, and the eavesdroppingdevice 109 can include one or more transceiver 115, 118, and 121,respectively. Each of the transceivers 115, 118, and 121 can transmitand receive a wireless OFDM signal on the OFDM wireless channel 112.

The wireless OFDM channel 112 can have unique characteristics betweenany two of the transceivers 115, 118, and 121. The uniquecharacteristics can be based on the location of each of the transceivers115, 118, and 121. As an example, the wireless OFDM channel 112 betweenthe transceiver 115 and the transceiver 118 has differentcharacteristics in comparison to the wireless OFDM channel 112 betweentransceiver 115 and transceiver 121 or between transceiver 118 andtransceiver 121.

In OFDM, a block of N complex valued QAM symbols, for example X=[X₀, X₁,. . . , X_(N-1)], can be mapped onto N subcarriers with the IFFToperation. The resulting signal can give the elements in a time domainrepresentation, x=[x₀, x₁, . . . , x_(N-1)]. In one embodiment, a sampleof this signal can be written as:

$\begin{matrix}{x_{m} = {\frac{1}{N}{\sum\limits_{k = 0}^{N - 1}\;{X_{k}\mspace{14mu}{e^{j\; 2\pi\;{km}\text{/}N}.}}}}} & (1)\end{matrix}$

After passing through the wireless channel, such as OFDM wirelesschannel 112, each subcarrier can be multiplied by the channel gain ofthe corresponding frequency, and received signal in frequency domain canbe given asY _(k) =H _(k) X _(k),  (2)where Y_(k) is the received symbol and H_(k) is the channel gain at thefrequency of kth subcarrier. The channel gain on the OFDM wirelesschannel 112 at a frequency can be dependent on the location of thecommunicating devices. For example, the channel gain at a frequency canbe based on the location of the transmitting device 103, the receivingdevice 106, and the medium between the transmitting device 103 and thereceiving device 106. As the location of the transmitting device 103 orreceiving device 106 changes, the OFDM wireless channel 112 between themcan also change.

In addition, the OFDM wireless channel 112 between two communicatingtransceivers is reciprocal. According to one example, thecharacteristics of the OFDM wireless channel 112 between the transceiver115 and the transceivers 118 have the same characteristics when viewedfrom either transceiver 115 or 118. Both the transceiver 115 and thetransceiver 118 can experience the same OFDM wireless channel 112throughout the coherence time of the medium. Further, transceiver 121cannot experience the same OFDM wireless channel 112 throughout thecoherence time of the medium between the transceivers 115 and 118.

In an SC-FDE system, artificial noise can be inserted on fadingfrequencies. Fading frequencies can be one or more frequency and/or oneor more bands of frequencies. The fading frequencies can be identifiedas having low channel gains. The fading frequencies can also beidentified as causing large power losses as compared to otherfrequencies. Information regarding which frequencies can be faded on anygiven channel will only be available to the receiver and transmittersharing the channel. An eavesdropping device cannot separate the actualsignal and artificial noise. Therefore, the data carrying signal fromthe eavesdropping device can be distorted with the artificial noise.Meanwhile, the transmitting device and receiving device can agree toignore artificial signal noise because of the channel reciprocity.

However, unlike in the SC-FDE system, where data symbols are carried inthe time domain, OFDM systems carry data symbols in the frequencydomain. Therefore, introducing a noise signal to an OFDM signal may notprevent eavesdroppers from detecting which frequencies are utilized andignoring transmissions on those frequencies. However, insertingartificial data as opposed to artificial noise can solve this deficiencyof artificial noise. For example, if a QPSK modulation is utilized, thetransmitting device 103 can select symbols from four complex numbers. Ifa particular region of a signal is filled with arbitrary samples whilethe remaining part can be filled with QPSK symbols, the eavesdroppingdevice 109 may be able to understand artificial noise carryingfrequencies through observation. However, the transmitting device 103can choose irrelevant QPSK symbols rather than artificial noise, whichis referred to herein as artificial data insertion. Further, thetransmitting device 103 can select the artificial data to reduce PAPR.In fact, a large PAPR can correspond to a large variance in the signal,which can be one of the major drawbacks in OFDM systems.

As PAPR increases for an OFDM signal over OFDM wireless channel 112, apower amplifier can output outside of its linear range, which can causesignal distortion. This distortion can degrade communicationperformance. This can be prevented by reducing the PAPR of a signal.Alternatively, this can be mitigated by utilizing a more expensive poweramplifier having a larger dynamic range in transceivers 115 and 118.When artificial data is added to the fading frequencies on a channel onOFDM wireless channel 112 for security, the transmitting device 103 canchoose the artificial data to reduce PAPR to mitigate PAPR problemswithout additional cost. For example, the transmitting device 103 canreduce the the PAPR without utilizing additional bandwidth on the OFDMwireless channel 112 beyond the fading frequencies utilized forsecurity.

By doing this, the transmitting device 103 can reduce PAPR and securethe communication to the receiving device 106 over OFDM wireless channel112 without consuming any extra resources. As a non-limiting example,the artificial data inserted OFDM signal in time domain can be expressedin equation 3 as follows:

$\begin{matrix}{{\hat{x}}_{m} = {\frac{1}{N}{\sum\limits_{k = 0}^{N - 1}\;{\left( {{a_{k}X_{k}} + {b_{k}{\overset{\sim}{X}}_{k}}} \right)e^{j\; 2\pi\;{km}\text{/}N}}}}} & (3)\end{matrix}$where {tilde over (X)}_(k) is the artificial data samples in frequency,a_(k) is 1 when k is the index of an information data, otherwise it is 0and b_(k) is 1 when k is the index of an artificial data, otherwise itis 0. Then we can form our objective function as,

$\begin{matrix}{{\overset{\sim}{X}}_{k} = \left. \underset{{\overset{\sim}{X}}_{k}}{\arg\mspace{14mu}\min}\mspace{14mu}||\hat{x} \right.||_{\infty}} & (4) \\{{{subject}\mspace{14mu}{to}\mspace{14mu}{\overset{\sim}{X}}_{k}} \in \Gamma} & (5)\end{matrix}$where ∥{circumflex over (x)}∥∞ represents the infinite norm operationand ┌ is the set of modulation symbols, e.g., {e^(jπ/4), e^(j3π/4),e^(−j3π/4), e^(−jπ/4)} for QPSK type of modulation.

In this way, transmitting device 103 can reduce the PAPR and secure theOFDM wireless channel 112 to prevent attacks by the eavesdropping device109. For example, the transmitting device 103 can prevent theeavesdropping device 109 from determining the genuine data because theeavesdropping device 109 cannot determine which frequencies are carryingthe artificial data.

According to one embodiment, the transmitting device 103 and a receivingdevice 106 are identical devices. The receiving device 106 transmitsdata over the OFDM wireless channel 112 to the transmitting device usingthe security and PAPR reduction techniques discussed herein. Forexample, the receiving device 106 can transmit artificial data chosen toreduce PAPR in frequencies that fail to meet a threshold and transmitgenuine data in the remaining frequencies. The transmitting device 103receives the wireless transmission over the OFDM wireless channel 112from the receiving device 106 using the techniques discussed herein. Forexample, the transmitting device 103 determines which frequencies failto meet the threshold and discard data on those frequencies.

With reference to FIG. 2A, shown is an illustration of the fadingfrequencies of the OFDM wireless channel 112 as seen by the transceivers115 and 118 according to various embodiments. The OFDM wireless channel112 as seen by transceivers 115 and 118 includes genuine datafrequencies 203 and artificial data frequencies 206. The transmittingdevice 103 and the receiving device 106 can sense the frequencies havingsignal characteristics, such as signal strength, that fails to meet thethreshold.

The transmitting device 103 and the receiving device 106 sense thestrength of the signal using transceivers 115 and 118. The transmittingdevice 103 and the receiving device 106 can identify those frequenciesas artificial data frequencies. In communications, the transmittingdevice 103 and the receiving device 106 can use the frequencies meetingthe threshold signal strength to carry genuine data and use thefrequencies failing to meet the threshold signal strength to carryartificial data.

With reference to FIG. 2B, shown is an illustration of the fadingfrequencies of the OFDM wireless channel 112 as seen by the transceiver121 according to various embodiments. The eavesdropping device 109 canreceive the OFDM wireless data transmitted by either transmitting device103 or receiving device 106. However, the eavesdropping device 109experiences different fading frequencies as compared to the transmittingdevice 103 and the receiving device 106 when receiving the OFDM wirelessdata. The OFDM wireless channel 112 as seen by transceivers 121 and 118cannot differentiate between genuine data frequencies 212 and artificialdata frequencies 215.

FIGS. 3 and 4 illustrate measured results according to an exampleembodiment. In this example embodiment, the multiple parameters can bedetermined. For example, QPSK can be utilized for modulation, a numberof subcarriers can be determined as 32, a 16-tap Rayleigh channel can beused for having the required selectivity in frequency, the averagechannel power can be normalized to 1, and one of three differentthreshold values, 0.1, 0.2, and 0.3, can be chosen in order to selectartificial data insertion frequencies. According to one example, thethresholds of 0.1, 0.2, and 0.3 correspond to utilizing of 9%, 18%, or26% respectively for spectral resource for artificial data based on theperformed simulations.

FIG. 3 illustrates a bit error rate for a variety of users andthresholds according to the example embodiment. Bit-error-rate (BER)results for a legitimate user using receiving device 106, Bob, and aneavesdropper using eavesdropping device 109, Eve, are shown in FIG. 3.The receiving device 106 has a lower error probability rate thanstandard communications because the fading frequencies are used forartificial data insertion. This is because the majority of bit errorsthat occur in OFDM can be within data transmitted over the fadingfrequencies. In contrast in FIG. 3, the eavesdropping device 109 has alarge BER even for high signal-to-noise ratio (SNR) values. For example,the BER does not noticeably reduce as Eb/No (dB) increases for thesignal sensed by the eavesdropping device 109 at any threshold level. Inaddition, the transmitting device 103 can use a larger threshold candegrade BER performance of the eavesdropping device 109 while enhancingBER performance of the receiving device 106 at the expense of morespectral resource usage.

FIG. 4 illustrates PAPR values for legitimate user Bob using receivingdevice 106 and Eve on eavesdropping device 109 at various thresholdvalues according to the example embodiment. The additional data can beselected to optimize PAPR. Shown are the PAPR curves for theaforementioned threshold values. The transmitting device 103 can use aflipping algorithm to find a sub-optimum artificial data set thatreduces PAPR. The complexity of this technique can be expressed asproportional to M×K where M is the number of modulation symbols and K isthe number of subcarriers used for artificial data in one symbol. Asshown in FIG. 4, as the threshold increases, the PAPR reduces. Inaddition, utilizing a flipping algorithm may not add significantcomplexity because a flipping algorithm for such optimization problemscan be implemented with low complexity. In other embodiments, morecomplex algorithms can be selected by the transmitting device 103 toobtain better PAPR reduction performance.

Referring next to FIG. 5A, shown is a flowchart that provide examples ofthe operation of a receiving device 106 (FIG. 1) according to variousembodiments. It is understood that the flowchart of FIG. 5A providesmerely an example of the many different types of functional arrangementsthat can be employed to implement the operation of the portion of thereceiving device 106 as described herein. As an alternative, theflowchart of FIG. 5A can be viewed as depicting examples of steps of amethod implemented in a receiving device 106 according to one or moreembodiments.

The process in FIG. 5A can be used to receive data with security in thephysical layer and a reduced PAPR on the transmitted signal according toone or more embodiments. In step 503, the process involves sensing thesignal strength of each of one or more frequencies on a wirelesschannel. For example, a transceiver 118 (FIG. 1) can be configured tocommunicate utilizing closely spaced orthogonal sub-carrier signals onparallel data frequencies. The transceiver 118 can be configured tosense the signal strength on each of the frequencies.

In step 506, the process involves identifying frequencies that meet athreshold signal strength on the wireless channel. In some embodiments,the process can involve identifying fading frequencies that fail to meetthe threshold signal strength. For example, the receiving device 106 cancompare the signal strengths measured in 506 to a threshold frequency.The receiving device 106 can identify the frequencies that meet thethreshold as frequencies to use to receive genuine data. The receivingdevice 106 can identify the frequencies that fail to meet the thresholdas frequencies to use for artificial data.

In step 509, the process involves receiving an OFDM transmission fromthe wireless channel. For example, the transceiver 118 can listen on theOFDM wireless channel 112 for a transmission and record the transmissionupon receipt. In step 512, the process involves processing data fromfrequencies that meet the threshold. The receiving device 106 canidentify data from frequencies that fail to meet the threshold asartificial data and processing data from the frequencies that meet thethreshold. The receiving device 106 can discard data received on thefrequencies failing to meet the threshold.

Referring next to FIG. 5B, shown is a flowchart that provide an exampleof the operation of a transmitting device 103 (FIG. 1) according tovarious embodiments. It is understood that the flowchart of FIG. 5Bprovides merely an example of the many different types of functionalarrangements that can be employed to implement the operation of theportion of the transmitting device 103 as described herein. As analternative, the flowchart of FIG. 5B can be viewed as depictingexamples of steps of a method implemented in a transmitting device 103according to one or more embodiments.

The process in FIG. 5B can be used to transmit data with security in thephysical layer and a reduced PAPR on the transmitted signal according toone or more embodiments. In step 515, the process can involve sensingthe signal strength of each of one or more frequencies on a wirelesschannel. For example, a transceiver 115 (FIG. 1) of the transmittingdevice 103 can be configured to communicate utilizing closely spacedorthogonal sub-carrier signals on parallel data frequencies. Thetransceiver 115 can be configured to sense the signal strength on eachof the frequencies.

In step 518, the process involves identifying frequencies that meet athreshold signal strength on the wireless channel. The transmittingdevice 103 can identify fading frequencies that fail to meet thethreshold signal strength on the OFDM wireless channel 112. For example,the transmitting device 103 can compare the signal strengths measured in515 to a threshold frequency. The transmitting device 103 can identifythe frequencies that meet the threshold as frequencies to use totransmit genuine data. The transmitting device 103 can identify thefrequencies that fail to meet the threshold as frequencies to use forartificial data.

In step 521, the process can involve generating a signal includingartificial data on frequencies that fail to meet the threshold andgenuine data on frequencies that meet the threshold requirement. Theprocess can also involve generating the artificial data as data thatminimized the PAPR of the generated signal. For example, thetransmitting device 103 can determine artificial data that will lower aPAPR value of a resulting signal when substituted for genuine data. Thetransmitting device 103 can also place artificial data into bandwidthfrequencies that, based on various real world factors, require greaterpower to or that have reduced quality or intensity at a correspondingreceiving device 106. As an example, the various real world factors caninclude the medium between the transmitting device 103 and the receivingdevice 106 and the distance between the transmitting device 103 and thereceiving device 106.

In step 524, the process can involve transmitting the resulting signalover the OFDM wireless channel. For example, the transmitting device 103can transmit the signal over the OFDM wireless channel 112. Thetransmitting device 103 can utilize the transceiver 115 to transmit thesignal to a receiving device 106.

FIG. 6 illustrates an example schematic block diagram of a computingarchitecture 600 that may be employed as either of the transceiversaccording to various embodiments described herein. The computingarchitecture 600 may be embodied, in part, using one or more elements ofa specific purpose processing circuit or computing device. The computingarchitecture 600 includes a processor 610, a random access memory (RAM)620, a Read Only Memory (ROM) 630, a transceiver 640, a memory device650, and an Input Output (I/O) interface 660. The elements of computingarchitecture 600 are communicatively coupled via one or more localinterfaces 602. The elements of the computing architecture 600 are notintended to be limiting in nature, as the architecture may omit elementsor include additional or alternative elements.

In various embodiments, the processor 610 may include or be embodied asa general purpose arithmetic processor, a state machine, or an ASIC, forexample. The processor 610 may include one or more circuits, one or moremicroprocessors, ASICs, dedicated hardware, or any combination thereof.In certain aspects and embodiments, the processor 610 is configured toexecute one or more software modules which may be stored, for example,on the memory device 650.

The RAM and ROM 620 and 630 may include or be embodied as any randomaccess and read only memory devices that store computer-readableinstructions to be executed by the processor 610. The memory device 650stores computer-readable instructions thereon that, when executed by theprocessor 610, direct the processor 610 to execute various aspects ofthe embodiments described herein.

As a non-limiting example group, the memory device 650 includes one ormore non-transitory memory devices, such as an optical disc, a magneticdisc, a semiconductor memory (i.e., a semiconductor, floating gate, orsimilar flash based memory), a magnetic tape memory, a removable memory,combinations thereof, or any other known non-transitory memory device ormeans for storing computer-readable instructions. The I/O interface 660includes device input and output interfaces, such as keyboard, pointingdevice, display, communication, and/or other interfaces. The one or morelocal interfaces 602 electrically and communicatively couples theprocessor 610, the RAM 620, the ROM 630, the memory device 650, and theI/O interface 660 so that data and instructions may be communicatedamong them.

In certain aspects, the processor 610 is configured to retrievecomputer-readable instructions and data stored on the memory device 650,the RAM 620, the ROM 630, and/or other storage means and copy thecomputer-readable instructions to the RAM 620 or the ROM 630 forexecution, for example. The processor 610 is further configured toexecute the computer-readable instructions to implement various aspectsand features of the embodiments described herein. In embodiments wherethe processor 610 includes a state machine or ASIC, the processor 610may include internal memory and registers for maintenance of data beingprocessed.

The transceiver 640 can be any one of transceiver 115, 118, or 121 (FIG.1). The transceiver 640 can transmit and receive data wirelessly onvarious frequencies. The transceiver 640 can also be configured to sensethe signal strength on each frequency of a wireless channel. Thetransceiver 640 can communicate utilizing wireless LAN radio interfaces;digital radio system, such as DAB/EUREKA 147, DAB+, Digital RadioMondiale, HD Radio, T-DMB, and ISDB-TSB; terrestrial digital TV systems,such as DVB-T and ISDB-T, terrestrial mobile TV systems, such as DVB-H,T-DMB, ISDB-T, and MediaFLO forward link; cellular system, such as 3G,4G, LTE, BWA, MBWA, and E-UTRA; and other wireless frequencies.

Therefore, the following is claimed:
 1. A system comprising: a memorydevice; and at least one computing device in communication with thememory device, the at least one computing device being configured to atleast: sense a respective signal strength for each of a plurality offrequencies of an orthogonal frequency division multiplexing (OFDM)wireless channel; determine a first set of the plurality of frequenciesthat meet a threshold signal strength and a second set of the pluralityof frequencies that fail to meet the threshold signal strength based atleast in part on the respective signal strength; and initiate atransmission of a data signal comprising a plurality of artificial datacorresponding to the second set of the plurality of frequencies.
 2. Thesystem of claim 1, wherein the data signal further comprises a pluralityof genuine data corresponding to the first set of the plurality offrequencies.
 3. The system of claim 1, wherein the plurality ofartificial data is generated to minimize a peak to average power ratio(PAPR) across the OFDM wireless channel.
 4. The system of claim 1,wherein the threshold is predefined.
 5. The system of claim 1, furthercomprising another at least one computing device, the other at least onecomputing device being configured to: sense the respective signalstrength for each of the plurality of frequencies of an OFDM wirelesschannel; determine the first set of the plurality of frequencies thatmeet the threshold signal strength and the second set of the pluralityof frequencies that fail to meet the threshold signal strength based atleast in part on the respective signal strength; and receive the datasignal and determine a plurality of genuine data based on the first setof the plurality of frequencies.
 6. The system of claim 5, wherein thethreshold is negotiated between the at least one computing device andthe other at least one computing device.
 7. A system comprising: amemory device; a remote device; a second remote device; and at least onecomputing device in communication with the memory device, the at leastone computing device being configured to at least: sense a respectivesignal strength associated with each of a plurality of frequencies of anorthogonal frequency division multiplexing (OFDM) wireless channel,wherein the respective signal strength associated with each of theplurality of frequencies utilized by the OFDM wireless channel is uniqueto the OFDM wireless channel between the at least one computing deviceand the remote device, wherein a respective second signal strengthassociated with each of the plurality of frequencies utilized by asecond OFDM wireless channel between the at least one computing deviceand the second remote device differs from the respective signal strengthassociated with each of the plurality of frequencies utilized by theOFDM wireless channel; identify a subset of the plurality of frequenciesmeeting a threshold signal strength based at least in part on therespective signal strength of each of the plurality of frequencies;receive a wireless signal on the OFDM wireless channel; and determine aplurality of data from the wireless signal.
 8. The system of claim 7,wherein the at least one computing device is further configured to atleast extract the plurality of data from a plurality of modulatedsymbols.
 9. The system of claim 7, wherein the OFDM wireless channel isbetween the at least one computing device and a remote device, and thewireless signal received is from the remote device.
 10. The system ofclaim 7, wherein the plurality of data corresponds to the subset of theplurality of frequencies meeting the threshold signal strength.
 11. Amethod comprising: sensing, via at least one computing device, arespective signal strength associated with each of a plurality offrequencies utilized by an orthogonal frequency division multiplexing(OFDM) wireless channel; identifying a subset of the plurality offrequencies failing to meet a threshold signal strength; generating aplurality of artificial data; and transmitting, via the at least onecomputing device, a signal comprising the plurality of artificial dataon the subset of the plurality of frequencies.
 12. The method of claim11, wherein the respective signal strengths on the OFDM wireless channelare exclusively sensible by the at least one computing device and aremote device.
 13. The method of claim 11, further comprising: sensing,via at least one second computing device, the respective signal strengthassociated with each of the plurality of frequencies utilized by an OFDMwireless channel; identifying a second subset of the plurality offrequencies that meet the threshold signal strength; receiving, via theat least one second computing device, the signal on the OFDM wirelesschannel; and determining a plurality of data from the signal, theplurality of data comprising a plurality of genuine data and theplurality of artificial data.
 14. The method of claim 11, wherein thesignal further comprises a plurality of genuine data on a remainder offrequencies of the plurality of frequencies.
 15. The method of claim 14,wherein the method further comprises generating the signal by insertingthe subset of the plurality of frequencies and the plurality of genuinedata into a plurality of modulated symbols.
 16. The method of claim 11,wherein the plurality of artificial data is generated to minimize a peakto average power ratio (PAPR) of the OFDM wireless channel.
 17. Themethod of claim 16, wherein the PAPR is minimized using a flippingalgorithm.
 18. The method of claim 11, wherein the subset of theplurality of frequencies is identified based at least in part on therespective signal strength of each of the plurality of frequencies. 19.The system of claim 7, wherein the plurality of data comprises aplurality of artificial data.
 20. The system of claim 19, wherein theplurality of data further comprises a plurality of genuine data.